Japan...
If both Germany and the USA get the idea that Japan wants such places as Tsingtao, Manila, and a few other tid-bits in the Pacific (a not unreasonable belief) the something just might happen. It would have to be very threatening from the American's point of view, given the US isolationism, but such a situation could get the ball rolling.
I can see Germany (under a competent foreign minister) reacting to a threat to America's Pacific territories by extending an offer of alliance. The terms would be very specific, comitting either of them to defend the other's Pacific posessions IF they were attacked--a strictly defensive and local deal. The USA gains security against Japanese snagging the Phillipines and similar territory, Germany gets the USA slightly brought into the alliance system.
Britan allies with Japan just after that--once again a defensive deal only.
Then--Japan gets the supply of 12" guns that it wants, allowing Satsuma to be the first all big gun battleship. Now things get hairy...